Errai Framework main website states that Errai 4.x should be targeted to Java 7.

When I do that and attempt a GWT Compile, I receive and UnsupportedClassVersionError error, stating 'Unsupported major.minor version 52.0'... which is basically saying it should be Java 8?

So my question is as basic as this... is Errai 4.x Java 7 or 8? If 7, how can I avoid the UnsupportedClassVersionError? I would like to use Java 7, as I want to use on Google AppEngine Standard (since Flex seems to still have issues).